CUDA only works on nVidia GPUs. Otherwise everything is normal.
Ok. But can't i installated any GPU accellarator?
Because I can not see the preview in real time ...
GPU has nothing to do with that. I'm pretty sure After Effects has known/unknown issues with El Capitan 10.11.
A quick google search should net you some useful information
As I said, there are known issues with the operating system you have and After Effects
Why? I don't know. Because sh*t happens, I guess.
There is tons of discussion about this all over the web.
I've gone ahead and done a simple google search for you.
These threads will tell you much more than I am able to.
I hope it helps.